5-car 80x have a VCB (VCB1) between the pantograph and 25kV bus line (which is on the roof - you can see the curly connections between the vehicles), and another VCB (VCB2) between bus line and transformer. There are 2 transformers on 5-car 80x, on each driving trailer, so there will be 3 VCBs in operation at any one time - VCB1 between whichever pan is raised and the bus line, and 2 VCB2s (1 on either driving trailer) between the bus line and the transformers. If you're sat at the rear and the pan is raised on the front, you'll hear VCB2 opening at the neutral section.
9-car 80x has another VCB, VCB3, on the TpS vehicle as there is another transformer on this vehicle (the p in TpS standing for 'power'). It's below sole bar level so you don't hear it so readily.
Having all these different VCBs means that if there is a transformer fault, then the VCB2 (or VCB3 on a 9-car) local to it will open, and the train can run off the remaining transformer(s). If there was only VCB1, then a fault on one transformer which caused VCB1 to open would mean that the other transformer would also lose power.
